What cultural faux pas should I try to avoid making in Kopavogur?

"In Kopavogur, it's considered rude to show up unannounced at someone's home. Always make sure to call ahead and arrange a visit. Avoid comparing Iceland to other Scandinavian countries, as Icelanders are proud of their unique culture and heritage. Do not litter or disrespect the environment. Icelanders are very environmentally conscious and take great pride in their country's natural beauty. Avoid discussing whaling. It's a controversial topic in Iceland and can lead to heated debates. Do not expect to haggle or bargain in shops or markets. This is not a common practice in Iceland and can be seen as disrespectful. Avoid being overly loud or boisterous in public places. Icelanders tend to be reserved and value their personal space. Do not assume everyone speaks English. While many Icelanders are multilingual, it's polite to ask if they speak English before starting a conversation. Avoid making jokes about elves or trolls. Many Icelanders take their folklore seriously and may not appreciate the humor. Do not expect to pay with cash. Iceland is a largely cashless society and most transactions are done electronically. Avoid being late. Punctuality is important in Icelandic culture. Do not disrespect the Icelandic language. It's an important part of their cultural identity and Icelanders are proud of their language," mentioned another expat when asked about moving to Kopavogur, Iceland.